How many transformers
- Thread starter trevmai
- Start date
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Potatoe Potato.
It used to be common to fit say 2 or 3 per tranny.
Trannies came down in price, so it is sensible to fit one per light.
In shops, restaurants etc it is common to fit a few HUGE trannies with 1.5mm (atleast) drops to the lights.
If you do fit several lights to a tranny, make sure you star wire, and use cables of a suitable size.
Be aware that a 50w lamp will draw almost 5 amps. That is actually a fair amount of current, and can cause cables/terminations to overheat. This sort of current, and remembering we are dealing with 12v, can have an adverse effect on volt drop - even just a small 1 to 2 volt drop on 12v can decrease lamp life by half!
It used to be common to fit say 2 or 3 per tranny.
Trannies came down in price, so it is sensible to fit one per light.
In shops, restaurants etc it is common to fit a few HUGE trannies with 1.5mm (atleast) drops to the lights.
If you do fit several lights to a tranny, make sure you star wire, and use cables of a suitable size.
Be aware that a 50w lamp will draw almost 5 amps. That is actually a fair amount of current, and can cause cables/terminations to overheat. This sort of current, and remembering we are dealing with 12v, can have an adverse effect on volt drop - even just a small 1 to 2 volt drop on 12v can decrease lamp life by half!
Sorry Lectrician, don't understand that last bit. If the volt drop is 2v then the lamp is running on 10v. It will be dimmer than those getting a full 12v but (I would have thought) the lamp life would be longer rather than shorter as a result.
Or is it me thats being dim?
TTC
Or is it me thats being dim?
TTC
Taylortwocities said:
In a TH lamp, the halogen serves to return tungsten that has been 'boiled off' back to the filament, this process requires a high lamp temperature to function correctly, granted the rate of tungsten evaporation will be lower when the lamp is run at lower power, but its accepted that this won't totally make up for the lack of the halogen cycling process and lamp life will be reduced
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B
breezer
Halogens are not normal lamps there is a "halogen cycle"
simple version
filament gets white hot
lamp lights
small bits of tungsten get burnt off and float around and land back on filament
if lamp does not get white hot small bits of tungsten dont come off (or not very well) filament burns out
halogen lamps rely on the fact the filament gets white hot to work
simple version
filament gets white hot
lamp lights
small bits of tungsten get burnt off and float around and land back on filament
if lamp does not get white hot small bits of tungsten dont come off (or not very well) filament burns out
halogen lamps rely on the fact the filament gets white hot to work
No - power is the same whichever side of the transformer you are.
Power is the product of voltage and current (P = VxI)
50W @ 240V = 0.21A
50W @ 12V = 4.2A
Power is the product of voltage and current (P = VxI)
50W @ 240V = 0.21A
50W @ 12V = 4.2A
0.2 amps on the MAINS supply TO the transformer, but 4.2 amps FROM transformer TO lamp.
no.. the mains amps will be less than the amps comming out of the transformer..
this is just the way transformes work.. less volts out, but more amps out..
at 50W ( and asuming a supply voltage of exactly 240V ), you can theoretically have 28.8 but in reality you can have about 25 lamps on one 6A breaker ( allowing for transformer losses, cable losses and variations in supply voltage )
going back to the under / over voltage...
if the ideal operating voltage is 12v, then is there a way to regulate AC to exactly 12v since the output voltage will vary with input voltage..?
this is just the way transformes work.. less volts out, but more amps out..
at 50W ( and asuming a supply voltage of exactly 240V ), you can theoretically have 28.8 but in reality you can have about 25 lamps on one 6A breaker ( allowing for transformer losses, cable losses and variations in supply voltage )
going back to the under / over voltage...
if the ideal operating voltage is 12v, then is there a way to regulate AC to exactly 12v since the output voltage will vary with input voltage..?
Electronic tranformers do this - thats what they are designed to do.
They give out a guaranteed 11.4v (I recall) independent of the supply voltage / voltage drop. They also do not output AC - well they do, but not 50Hz - they give out a really high frequency AC which is why most DVM's can't measure the voltage.
They give out a guaranteed 11.4v (I recall) independent of the supply voltage / voltage drop. They also do not output AC - well they do, but not 50Hz - they give out a really high frequency AC which is why most DVM's can't measure the voltage.
Without a calc, I can recall that 1200watt is 5amps.
1200 / 50.........24 (12 devided by a half).
So, 24 50 watt lamps. This takes no account of transformer losses (which are negligeable with electrnic tranny.
Remember - watts are watts. Current and volts may change, but you don't get something for nothing in this world - everything has an equal and opposite. 50 watt is 50 watt at whatever voltage.
1200 / 50.........24 (12 devided by a half).
So, 24 50 watt lamps. This takes no account of transformer losses (which are negligeable with electrnic tranny.
Remember - watts are watts. Current and volts may change, but you don't get something for nothing in this world - everything has an equal and opposite. 50 watt is 50 watt at whatever voltage.
As power (Watts) = Voltage X Current....
24 X 50W = 1200W
1200W / 230V = 5.217... Amps
That sounds ok. for a 1.5mm cable on the 230Volt side of individual transformers.
However, if you wish to connect them all to one 12V power supply in parallel....
24 X 50W = 1200
1200W / 12V = 100 Amps. (yes, 100 Amps!)
If you try it, make sure you get one of these first....
http://www.freefoto.com/preview.jsp?id=28-02-12&k=Scania+94D+260+Fire+Engine
24 X 50W = 1200W
1200W / 230V = 5.217... Amps
That sounds ok. for a 1.5mm cable on the 230Volt side of individual transformers.
However, if you wish to connect them all to one 12V power supply in parallel....
24 X 50W = 1200
1200W / 12V = 100 Amps. (yes, 100 Amps!)
If you try it, make sure you get one of these first....
http://www.freefoto.com/preview.jsp?id=28-02-12&k=Scania+94D+260+Fire+Engine
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